The present invention relates to a satellite navigation method for a mobile station, wherein the geographic position of the mobile station is determined in the mobile station by means of a receiving and evaluating unit for the reception and evaluation of satellite navigation signals.
The invention relates in particular to a satellite navigation method for a terrestrial (earth-based) mobile station, that is, a station that is mobile on the earth's surface (dry land and/or water) wherein the station comprises at least one receiving and evaluating arrangement for the reception and evaluation of the available satellite signals of the navigation satellites, for example, according to the American GPS system and/or the Russian GLONASS system. With the GPS system, a precision of .+-.100 m (95%) can be accomplished for civilian applications in the determination of the geographic position of a mobile station if the satellite signals are evaluated directly. If it is necessary to determine the position more precisely, a differential navigation method is generally used, for example, the so-called DGPS ("Differential Global Positioning System").
During this process, stationary reference stations, so-called DGNSS reference stations are employed, each having a known geographic position. In such a reference station, the geometric or active ranges from the (satellite) receiving antenna to all receivable ("visible") navigation satellites are known at all times. When the satellite signals mentioned at the outset are received at the antenna, so-called pseudoranges from the receivable satellites emerge from the signal delay times. From the comparison of the pseudoranges with the known geometric ranges, standardized correction values are determined. These are emitted continuously or periodically over time by the reference station via known data links (radio channels). A mobile station can then receive the correction values, and the pseudoranges determined by the mobile station can be corrected with these correction values. With a differential satellite navigation method of this type, it is possible to accomplish a precision in the range of several hundred meters or even less for the mobile station when determining its position.
However, it is a drawback that such a standardized differential navigation method is technically complex for a terrestrial land application (navigation on the land surface). This is due to the fact that for a reliable transmission of the differential corrections (correction values), particularly in hilly and/or mountainous terrain, a plurality of (relay) transmitting stations are necessary to supply a mobile station with correction values at any time without shadowing of the data link (radio channel) from the DGNSS reference station to the mobile station taking place.
It is the object of the invention to provide a method of the generic type described above which permits an economical and reliable position determination for a mobile station by means of satellite navigation with a precision which corresponds to that of a differential satellite navigation method and without necessitating a so-called DGNSS reference station.